High pressure NMR Stucy of Unusual Magnetism and characteristic Superconductivity apperaing in Uru2Si2 and UPt3

Uru2Si2和UPt3中异常磁性和特征超导性的高压核磁共振研究

• 批准号: 14540344
• 负责人: KOHARA Takao
• 金额: $ 2.3万
• 依托单位: Graduate school of Material Science, Himeji Inst.of tech.
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (C)
• 财政年份: 2002
• 资助国家: 日本
• 起止时间: 2002 至 2003
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-14540344/
• 关键词: high pressure NMR; microscopic competition; concentrated; dilution refrigerator; superconducting energy gap; 5f電子系; 圧力誘起超伝導; 非BCS機構; NMR; NQR; 隠れた秩序変数

The purpose of this subject is the following two issues : one is to get the information on the superconducting energy gap appearing in the antiferromagnetic region of URu2Si2 under high pressure) the other is to get the origin on unusually small magnetic moment by Pt NMR in UPt3, where spin fluctuations are strongly suppressed by high pressure. For the purpose of getting the detailed structure of gap, we tried to measure the temperature dependence of nuclear spin relaxation rate down to 20 thru 30mK by a dilution refrigerator, because the superconducting transition temperature decreases drastically from 1.5 K with increasing pressure. However, the lowest temperature obtained in our dilution ref. is about 250 mK because of limited cooling power and a big high pressure cell (20mm in a diameter and 90mm in height). So we have to design the improved high pressure cell for the further NMR/NQR measurement at low temperatures. Fortunately, we could find weak 29Si NMR signal in the antiferromagnetic region of URu2Si2 attached in high pressure cell. Moreover, high pressure Si NMR revealed that the antiferromagnetic region obtained by applying high pressure is magnetically quite uniform with magnetic moment, of 0.3 μB. Secondly, we tried to purchase enriched 195 Pt for high pressure NMR measurement, because just a very weak Pt signal could be expected in the high pressure cell, if exists. The nominal (chemical) purity in enriched Pt was, however, 99.0 % thru 99.3 % for French and US products, though the enrichments were 99.8%. In order to have the sample of almost the same quality compared with the previously reported samples, more than 99.9 % in chemical purity is necessary at least. So we gave up to prepare UPt3 of high quality using enriched Pt. (290 words)

本课题的目的是以下两个问题：一是获取高压下URu 2Si 2反铁磁区域出现的超导能隙信息），二是通过UPt 3中的Pt核磁共振得到异常小磁矩的起源，其中自旋涨落被高压强烈抑制。由于超导转变温度从1.5K开始随压力的增加而急剧下降，为了得到能隙的详细结构，我们尝试用稀释制冷机测量了20 ~ 30 mK范围内核自旋弛豫速率随温度的变化。然而，在我们的稀释参考中获得的最低温度约为250 mK，因为有限的冷却功率和大的高压池（直径20 mm，高度90 mm）。因此，我们必须设计改进的高压池，以进一步在低温下进行NMR/NQR测量。幸运的是，我们可以在高压电池中的URu_2Si_2的反铁磁区找到较弱的~（29）Si NMR信号。高压硅核磁共振表明，高压下得到的反铁磁区磁性均匀，磁矩为0.3 μB。其次，我们试图购买用于高压NMR测量的富集的195 Pt，因为如果存在的话，在高压池中可以预期只有非常弱的Pt信号。然而，法国和美国产品的富集铂标称（化学）纯度为99.0%至99.3%，尽管富集度为99.8%。为了使样品的质量与以前报道的样品几乎相同，至少需要大于99.9%的化学纯度。因此，我们放弃了利用富集铂制备高质量UPt 3。(290字）

项目成果

T.Kohara: "New Aspects on URu_2Si_2 and CeTIn_5 (T=Rh,Ir,Co) observed by High Pressure NMR and NQR"Pramara -Jour.of Phys.-(Indian Academy of Sciences). 58. 755-760 (2002)

T.Kohara：“高压 NMR 和 NQR 观察到的 URu_2Si_2 和 CeTIn_5 (T=Rh,Ir,Co) 的新方面”Pramara -Jour.of Phys.-（印度科学院）。

K.Matsuda, Y.Kohori, T.Kohara et al.: "29Si NMR study of URu2Si2 under pressure"Physica B. 312-313. 504-505 (2002)

K.Matsuda、Y.Kohori、T.Kohara 等：“加压下 URu2Si2 的 29Si NMR 研究”Physica B. 312-313。

K.Matsuda: "^<29>Si NMR Study of URu_2Si_2 under Pressure"Physica B. 312-313. 504-505 (2002)

K.Matsuda：“压力下URu_2Si_2的^ 29 Si NMR研究”Physica B.312-313。

K.Matsuda, Y.Kohori, T.Kohara, H.Amitsuka, T.Matsumoto: "^<29>Si NMR study of Uru_2Si_2 under pressure"Physica B. 312-313. 504-505 (2002)

K.Matsuda、Y.Kohori、T.Kohara、H.Amitsuka、T.Matsumoto：“Uru_2Si_2在压力下的^ 29 Si NMR研究”Physica B.312-313。

Y.Iwamoto, K.Ueda, T.Kohara, Y.Kohori, V.S.Zapg, T.a.sayles, M.B.Maple, J.L.Sarrao: "NQR and NMR studies of heavy fermion Ce_<1-x>R_xRHIn_5 (R=Y,La)"

Y.Iwamoto、K.Ueda、T.Kohara、Y.Kohori、V.S.Zapg、T.a.sayles、M.B.Maple、J.L.Sarrao：“重费米子 Ce_<1-x>R_xRHIn_5 (R=Y,La) 的 NQR 和 NMR 研究